Method of flattening metal strip or sheet



March 2, 1965 R. K. HOLTZ 3,171,464

METHOD OF FLAT'I'ENING METAL STRIP OR SHEET Filed Sept, 4, 1962 2Sheets-Sheet 1 INVENTOR. Raymond. K Holt:

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METHOD OF FLATTENING METAL STRIP 0R SHEET Filed Sept. 4, 1962 2Sheets-Sheet 2 INVENTOR. Raymond K. l-lalfz H IS ATTORNEYS United StatesPatent Pennsylvania Filed Sept. 4, 1962, Ser. No. 221,185 9 Claims. (Cl.153-456) This invention relates to a method of flattening nonferrous andferrous metal strip or sheet, particularly aluminum, copper, brass andcarbon and alloy steel cold rolled strip and sheet in gauges about0.040" and lighter and in almost any width.

Ability to produce metal strip and sheet, particularly in large coils,with a high degree of flatness widthwise throughout substantially theirlength and in some cases, substantially perfect flatness, has been aproblem for some time. Many fabricators of metal parts and metalarticles require flat sheet and strip in order to meet specification andproduce a high quality article.

Heretofore, some rolled strip or sheet has been passed through rollerlevelers wherein it is flexed alternately between the work rolls of thelevelers to flatten same but these levelers have not been whollysuccessful for flattening the lighter gauges such as those 0.040" andthinner which are more difficult to roll fiat than the heavier gauges.Furthermore, flattening the lighter gauges on a roller leveler is moredifficult than flattening the heavier gauges for the lighter gauges areless prone to assume a radius of bend defined by the diameter of thework rolls of the leveler and by the positions of the upper work rollsrelative to the lower work rolls.

In roller levelling strip and sheet, the material is bent by the workrolls about its neutral axis where a zero bending stress is maintained.At the radii of the bends in the strip where yield stress is encounteredin the outside fibers ot the strip (tensile stress on the outsidesurface and compression stress on the inside surface of the bend), astress distribution results which decreases in a straight linerelationship from the tensile yield value at one outside fiber throughzero at the neutral axis to the compressive yield value at the otheroutside fiber. Decreasing the radius of the bend causes the yield stressto penetrate below the outside fibers or surfaces of the strip andincreases the amount of metal thicknesswise which has been stressedbeyond the yield point. However, two factors limit the amount one candecrease the radius of the bends which, in turn, limit from a practicalstandpoint the eifectiveness of a roller leveler on light gaugematerials. The first factor is that as the work roll diameters andcenter-to-ccnter spacing thereof are decreased to elfect a smaller bendradius, the leveler becomes mechanically weaker and unsuited forflattening the heavier gauges. Accordingly, the gauge range which can beaccommodated by a given leveler is limited and the machine is notattractive to a customer who is not able to justify purchase on a basisof light gauges alone.

The second factor is that the lighter gauges being less rigid than theheavier gauges tend not to assume the radius of the bends governed bythe work roll diameter and center-to-center spacing thereof.

Application of tension to the strip while it traverses a roller levelerovercomes mechanical limitations of design of the leveler by inducing anadditional stress to the strip which, when added to the stress generatedby bending of the strip around a portion of the work rolls of theleveler, has the same effect as decreasing the bend radius. Also,tension increases the apparent rigidity of the metal strip and insuresthat it conforms to the Work roll radius of the leveler duringflattening and improves the effectiveness of the leveler adjustments.This tension is applied longitudinally of the strip and substantially inthe direction of the path of travel of the strip through the rollerleveler.

The amount of tension used for flattening a particular strip or sheet isdetermined by taking into account stress/ strain characteristics of themetal and the relationship between the gauge of the metal to beflattened and the work roll diameter of the roller leveler.

To achieve a high degree of flatness in the strip, adequate inspection,preferably continuous inspection, of the strip issuing from the tensionleveling part of the apparatus is highly important to afford anopportunity to regulate positions of the work rolls of the leveler andamounts of tension applied to the strip and thereby correct unflattenedportions or segments of the strip. Additionally, the strip should be atZero tension during inspection because it the material is not quiteflat, a small amount of tension therein may make the strip appear to beflat.

My invention provides a method of flattening metal strip and sheet inlong continuous lengths wherein the stnip is subjected to tension duringflattening and then is made available at substantially zero tension forsubstantially continuous inspection, after which it is wound into a coilor cut to length. Specifically, my method for flattening strip or sheetcomprises passing a continuous length of the strip along a path oftravel through a roller leveler and through a first means for engagingthe strip and operable to place a forward tension thereon. A forwardtension is placed upon the strip While passing it through the rollerleveler and to the first means after which it is advanced from the firstmeans further along the path of travel and conveyed over an inspectiontable and to a second means for engaging the strip and moving it overthe inspection table. This second means is operated relative to thefirst means so that the strip is under substantially zero tension duringits travel over the inspection table. Then the strip is further advancedfrom the second means and Wound into a proper coil while subjecting itto tension which assists to produce the neat coil.

The second means is operated relative to the first means so as toproduce a loop in the strip between the first means and the inspectiontable or between the inspection table and it.

To place a back tension on the strip on the entry side of the rollerleveler, I pass the strip through a third means positioned in advance ofthe entry end of the roller leveler and so operate this third meansrelative to the roller leveler and/or the first means that the strip issubjected to back tension between the third means and the rollerleveler.

My apparatus for flattening metal strip and sheet cornprises a rollerleveler positioned for receiving the strip from a feed means and a firsttension means on the exit side of the roller leveler and in tandemtherewith so that the strip travels through the roller leveler and thefirst tension means sequentially. This first tension means is operablefor generating a forward tension on the strip between the roller levelerand it. On the exit side of the first tension means is an inspectiontable for travel of the strip thereover. A second tension means is onthe exit side of the inspection table for engaging the strip andadvancing it over the inspection table. This second tension means isoperable relative to the first tension means so that the strip is undersubstantially zero tension in its travel over the inspection table.

Between the exit end of the first tension means and the entry end of theinspection table is a pit for receiving a loop in the strip. This pitmay also be located between the inspection table and the second tensionmeans.

On. the exit side of the second tension means is a winding reel forwinding the strip into the coil and for placing a tension on the stripbetween the second tension means and the reel to produce the propercoil.

Between the feed means and the roller leveler is a third tension meansfor engaging the strip and for travel of the strip therethrough. Thisthird tension means is operable relative to the roller leveler and/ orthe first tension means for generating a back tension in the stripbetween the roller levelerand it. I e V In the accompanying drawings Ihave shown a preferred embodiment of my invention in which:

- FIGURE 1 is a plan view of apparatus foreffecting flattening of metalstrip and sheet and on which I practice my method for flattening'thestrip and sheet;

of FIGURE 1; and

FIGURE 3 is a side elevation view of a three-roll bridle and a slopinginspection table which can be used in the in alignment and arranged intandem so that strip passes sequentially through each from the payoffreel 1 through to the winding reel 10.:

'15 FIGURE 2 is a side elevation view of the apparatus The payoff reel 1mounts a coil of metal strip 11 and delivers same to the entry end 12 ofthe first bridle 2 which comprises four rolls horizontally mounted,three of which are driven by motors 13. The rolls of the first bridleare arranged substantially in tandem with the two end rolls 14 and 15 ofthe four being slightly below the two center rolls 16 and 17. The stripenters the first bridle over a billy roll 13 and travels around the leftcenter roll 16 which is motor driven, then around the left end'roll 14which is an idler one, next beneath the two center rolls 16 and 17 andaround the right end roll'15, motor driven, from which it goes aroundthe right center roll 17 and then passes over the exit end 19 of thefirst bridle into the roller leveler 3.

This roller leveler 3 is of conventional construction and, therefore,further description thereof is deemed unnecessary other than to pointout that it has work rolls 2% which are driven by a motor 21, which forma labyrinth path of travel 22 therethrough and which alternately flexthe strip to flatten same. 7 i

' From the exit end 23 of the roller leveler, the strip advances intothe second bridle 4 whose construction is substantially the same as thefirst bridle. This second bridle likewise has three motor driven rolls24, 25 and 26 and one idler roll 27 :and the path of travel of" thestrip through the second bridle is the same'as the path of travelthrough the first bridle. I p I The driven rolls 24, 25 and 26of thesecond bridle are so powered by the motors connected thereto that theygenerate a forward tension upon the strip in its travel from the firstbridle through the roller leveler to the second bridle. A conventionalelectric control (not shown) eifects operation of the second bridle toprovide this forward tension.

I neat coil...

The driven rolls 15, 16 and 17 of the first bridle are so powered by themotors 13 relative to the roller leveler and/ or the second bridle thatthey produce a back tension upon the strip in its travel from thefirst'br'idle to the roller leveler. The electric control brings aboutoperation of the first bridle to obtain this back tension.

On the exit end 28 of the second bridle is a first roller conveyor 29comprising a plurality of idler rolls 3% which form an arcuate path oftravel for the strip extending from a horizontal plane to avertical'plane which leads into the pit 5. V

In the pit, the strip forms a loop 31 which lies in a 4 substantiallyvertical plane disposed substantially parallel to the path of travel ofthe strip through the apparatus. On the exit end 32 of the pit is asecond roller conveyor 33 ..substantially the sameas the first rollerconveyor With its idler rolls arranged to form an arc'uate path oftravel for the strip leaving the pit so that it is guided from avertical plane into a horizontal plane for advancementto the inspectiontable.

, The second roller conveyor directs the strip onto the inspectiontable. 6 which comprises a bed 34 disposed horizontallyv to the surfaceof the level 35 on which the apparatus is'lo'cated. This bed preferablyis precisely flat to provide a properreference for determining thedegree of flatness in the strip, V

From the exit end of the inspection table the strip travels 'into thethird bridle 7 which comprises three rolls 36, 3'7 and 38 rotatablydriven by motors 39. These three rolls of the third bridle are arrangedin a V configuration with the entry roll 36 being disposed above thecenter roll 37 and the exit roll 38-likewise disposed above the centerroll. The strip travels around the inside of entry roll 36, then aroundthe bottom roll 37 and up and around and over the inside of the exitroll 38.

The rolls of the third bridle 7 are so powered by the motors 39 relativeto the second bridle that they produce the loop 31 in the strip in thepit and assure that the strip is under substantially zero tension duringits travel across the inspection table. The conventional electriccontrol regulates operation of the third bridle relative to theoperation of the second bridle 4 to form the loop in the pit 5 andpresent the strip at substantially zero tension in its travel across theinspection table 6.

From the, third bridle the strip progresses through a shear 8 whichcrops off ends of the coil should such cropping be required. V

Next, the strip travels'through a deflector roll assembly 9 whichcomprises two rolls 40 and 41 positioned so that their axes of rotationlie in a plane-disposed diagonally to the path of travel of the stripthrough the apparatus.

The rolls are adjacent one another whereby the strip travels overanupper surface of the lower roll 40 and across an under surface of theupper roll 41 and then onto the winding reellt). 1 I r The winding reelis driven by a motor (not shown) which generates a tension in the stripbetween the third bridle and the reel so that the strip can be woundinto a In. order to present the strip for inspection at substantiallyzerotension, it is highly desirable that the loop 31 be formed in orderto isolate the tension leveling appal ratus (the first and secondbridles and the roller leveler) loop permits use of diiferent amounts oftension for flattening than for rewinding the strip into a coil.

' .While non-flatness of a stripsedges is best judged by conveying itover a flat horizontal surface, non-flatness in'thecenter portion of thestrip is best judged on a substantially 'vertical strip pass line suchas an egress portion of the strip as it issues from the loop.Accordingly, the loop performs a function .of placing the strip in agood positionfor' inspection of central portions of the strip.

.When flattening lightgauges such as 0.010" and thinner, the weight ofthe strip in the loop, which, may be of considerable depth for variousreasons such as the speed of operation of the apparatus, can produce asufficient tension to obscure irregularities in flatness of the stripand prevent adequate inspection when the light strip is conveyed acrossa horizontal inspection table. Additionally, friction between the stripand the table also obscures the irregularities. .Under such conditions,a downwardly sloping inspection table 42 (FIGURE 3) on the exit side ofa three-roll second bridle 43and at the entrance to the loop ispreferable since such a table can be tilted to the exact angle requiredto minimize the effects of compressive feeding forces, table frictionand gravity all of which affect each other. An arm 44 connected to thelower end of the table 42 enables it to be tilted about its pivotmounting 45 to a given angle and thereby present light gauge strip atsubstantially zero tension for inspection.

The amount of tension which effects flattening of the strip during itstravel through the roller leveler in most cases is not the same as theamount of tension employed to rewind the strip into a coil. To flattenthe strip in its travel through the roller leveler, I employ an amountof tension which places it under a stress suificient to assist theroller leveler in effecting flattening. For example, about 100 pounds oftension per inch of strip width has been found satisfactory for somelight gauge materials.

The amounts of tension employed to wind the strip into a proper coil isin no way related to that required for tension leveling. Handling anduse requirements of the coils determine the amount of tension used forwinding the strip into these coils.

Conventional pinch roll stands driven by conventional motors can besubstituted for one or more of the bridles in my apparatus and performthe same functions therein as the bridles.

While I have shown and described preferred embodiments of my invention,it is understood that it may be otherwise embodied within the scope ofthe fOllOWing claims.

I claim:

1. In a method of flattening metal strip or sheet the inventioncomprising passing a continuous length of said strip along a path oftravel through a roller leveler and then through a first means forengaging said strip and operable to place a forward tension thereon,placing a forward tension upon said strip during passing same throughsaid roller leveler and through said first means, advancing said stripfrom said first means further along said path of travel and conveyingsame over an inspection table and to a second means for engaging saidstrip and moving same over said inspection table, operating said secondmeans relative to said first means so that said strip is undersubstantially zero tension during its travel over said inspection table.

2. The invention of claim 1 characterized by advancing said strip fromsaid second means and winding same into a coil.

3. In a method of flattening metal strip or sheet, the inventioncomprising passing a continuous length of said strip along a path oftravel through a first means for engaging said strip and advancing sameto a roller leveler, then passing said strip through said roller levelerand next through a second means for engaging said strip and operable toplace a forward tension thereon, placing a back tension upon said stripduring passing same from said first means to said roller leveler,placing a forward tension upon said strip during passing same throughsaid roller leveler and to said second means, advancing said strip fromsaid second means further along said path of travel and conveying sameover an inspection table and to a third means for engaging said stripand moving same over said inspection table, operating said third meansrelative to said second means so that said strip is under substantiallyzero tension during its travel over said inspection table.

4. The invention of claim 3 characterized by so operating said thirdmeans relative to said second means as to produce a loop in said stripbetween said second means and said inspection table, said loop lying ina substantially vertical plane disposed substantially parallel to saidpath of travel.

5. The invention of claim 4 characterized by advancing said strip fromsaid third means and subjecting same to tension while winding it into acoil.

6. In a method of flattening metal strip or sheet wherein the strip ispassed along a path of travel through a roller leveler and then througha first means for engaging said strip and operable to place a forwardtension thereon and wherein a forward tension is placed upon said stripduring passing same through said roller leveler and to said first means,the invention comprising advancing said strip from said first meansfurther along said path of travel and conveying same over an inspectiontable and to a second means for engaging said strip and moving same oversaid inspection table, operating said second means relative to saidfirst means so that said strip is under substantially zero tensionduring its travel over said inspection table.

7. The invention of claim 6 characterized by advancing said strip fromsaid second means and subjecting same to tension while winding it into acoil.

8. The invention of claim 6 characterized by so operating said secondmeans relative to said first means as to produce a loop in said stripbetween said first means and said inspection table, said loop lying in asubstantially vertical plane disposed substantially parallel to Saidpath of travel.

9. The invention of claim 6 characterized by so operating said secondmeans relative to said first means as to produce a loop in said stripbetween said inspection table and said second means, said loop lying ina substantially vertical plane disposed substantially parallel to saidpath of travel.

References Cited by the Examiner UNITED STATES PATENTS 1,940,939 12/33Cor-yell 29-547 2,316,801 4/43 McLaughlin et a1. 153-2 2,338,678 1/44Wilson 153-86 2,588,439 3/52 Ward 153-86 CHARLES W. LANHAM, PrimaryExaminer. WILLIAM J. STEPHENSON, Examiner.

1. IN A METHOD OF FLATTENING METAL STRIP OR SHEET THE INVENTIONCOMPRISING PASSING A CONTINUOUS LENGTH OF SAID STRIP ALONG A PATH OFTRAVEL THROUGH A ROLLER LEVELER AND THEN THROUGH A FIRST MEANS FORENGAGING SAID STRIP AND OPERABLE TO PLACE A FORWARD TENSION THEREON,PLACING A FORWARD TENSION UPON SAID STRIP DURING PASSING SAME THROUGHSAID ROLLER LEVELER AND THROUGH SAID FIRST MEANS, ADVANCING SAID STRIPFROM SAID FIRST MEANS FURTHER ALONG SAID PATH OF TRAVEL AND CONVEYINGSAME OVER AN INSPECTION TABLE AND TO A SECOND MEANS FOR ENGAGING SAIDSTRIP AND MOVING SAME OVER SAID INSPECTION TABLE, OPERATING SAID SECONDMEANS RELATIVE TO SAID FIRST MEANS SO THAT SAID STRIP IS UNDERSUBSTANTIALLY ZERO TENSION DURING ITS TRAVEL OVER SAID INSPECTION TABLE.